[C++] fix crash in DelayedSchedulerTest.avoidCallingDtorOfRun...
[C++] fix crash in DelayedSchedulerTest.avoidCallingDtorOfRun...

DelayedSchedulerTest.avoidCallingDtorOfRunnablesAfterSchedulerHasExpired
occasionally crashed because of an invalid free:

*** Error in `./g_UnitTests': double free or corruption (out): ...***
Aborted (core dumped)

Change-Id: Icba32fcd785f6b1ba979f3237dd40d34cc01a847

bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr